From 5e9970311fd52bc3015ef5b90dfef31a15bdc940 Mon Sep 17 00:00:00 2001
From: NepDisk <nepdisk@noreply.codeberg.org>
Date: Mon, 10 Feb 2025 18:09:29 -0500
Subject: [PATCH] repair 'Change scroller direction'

---
 src/p_setup.c |  1 +
 src/p_spec.c  | 38 +++++++++++++++++++++++++++++++-------
 2 files changed, 32 insertions(+), 7 deletions(-)

diff --git a/src/p_setup.c b/src/p_setup.c
index 6afb8d5ae..cf621d0dd 100644
--- a/src/p_setup.c
+++ b/src/p_setup.c
@@ -6167,6 +6167,7 @@ static void P_ConvertBinaryLinedefTypes(void)
 		case 435: //Change plane scroller direction
 			lines[i].args[0] = tag;
 			lines[i].args[1] = R_PointToDist2(lines[i].v2->x, lines[i].v2->y, lines[i].v1->x, lines[i].v1->y) >> FRACBITS;
+			lines[i].args[2] = AngleFixed(R_PointToAngle2(lines[i].v2->x, lines[i].v2->y, lines[i].v1->x, lines[i].v1->y)) >> FRACBITS;
 			break;
 		case 436: //Shatter FOF
 			lines[i].args[0] = sides[lines[i].sidenum[0]].textureoffset >> FRACBITS;
diff --git a/src/p_spec.c b/src/p_spec.c
index 20c4fdc68..0899066be 100644
--- a/src/p_spec.c
+++ b/src/p_spec.c
@@ -3172,10 +3172,15 @@ boolean P_ProcessSpecial(activator_t *activator, INT16 special, INT32 *args, cha
 				scroll_t *scroller;
 				thinker_t *th;
 
-				fixed_t length = R_PointToDist2(line->v2->x, line->v2->y, line->v1->x, line->v1->y);
-				fixed_t speed = args[1] << FRACBITS;
-				fixed_t dx = FixedMul(FixedMul(FixedDiv(line->dx, length), speed) >> SCROLL_SHIFT, CARRYFACTOR);
-				fixed_t dy = FixedMul(FixedMul(FixedDiv(line->dy, length), speed) >> SCROLL_SHIFT, CARRYFACTOR);
+				fixed_t speed;
+				angle_t angle;
+				fixed_t dx;
+				fixed_t dy;
+
+				speed = args[1] << FRACBITS;
+				angle = FixedAngle(args[2] << FRACBITS) >> ANGLETOFINESHIFT;
+				dx = FixedMul(FINECOSINE(angle), speed) >> SCROLL_SHIFT;
+				dy = FixedMul(  FINESINE(angle), speed) >> SCROLL_SHIFT;
 
 				for (th = thlist[THINK_MAIN].next; th != &thlist[THINK_MAIN]; th = th->next)
 				{
@@ -3183,11 +3188,30 @@ boolean P_ProcessSpecial(activator_t *activator, INT16 special, INT32 *args, cha
 						continue;
 
 					scroller = (scroll_t *)th;
-					if (!Tag_Find(&sectors[scroller->affectee].tags, args[0]))
+
+					const taglist_t* taglist = (scroller->type == sc_side)
+						? &sides[scroller->affectee].line->tags
+						: &sectors[scroller->affectee].tags;
+
+					if (!Tag_Find(taglist, args[0]))
 						continue;
 
-					scroller->dx = dx;
-					scroller->dy = dy;
+					switch (scroller->type)
+					{
+						case sc_carry:
+						case sc_carry_ceiling:
+						{
+							scroller->dx = FixedMul(-dx, CARRYFACTOR);
+							scroller->dy = FixedMul(dy, CARRYFACTOR);
+							break;
+						}
+						default:
+						{
+							scroller->dx = dx;
+							scroller->dy = dy;
+							break;
+						}
+					}
 				}
 			}
 			break;